The U.S. National Electrical Code (NEC) (Article 240) requires that conductors such as wire, cable, bus bars, and the like, be protected against overcurrent in accordance with their ampacities, unless specifically exempted for a specific application. Overcurrent, generally caused by short circuits, can produce extreme heat and burning, smoke, and other dangerous conditions in conductors connected to battery systems.
However, overcurrent protection is not being accomplished in many telecommunication applications for several reasons. One primary reason for this is that the NEC, under Article 90-2(b)(4), does not cover “Installations of communications equipment under the exclusive control of communications utilities located outside or in building spaces used exclusively for such installations”. This has led to the general use of unfused batteries in communications.
Many municipalities have determined that the exemption under Article 90-2(b)(4) of the NEC does not apply to shared facilities (co-location), customer premise equipment, or other situations where failures in equipment may affect other areas or personnel. A typical situation may involve a tenant improvement for a cellular base station that could expose people working in the building to the effects of a battery short circuit event. Unfortunately, there is a general lack of suitable overcurrent protection devices, such as fuses and circuit breakers, that can be effectively applied to large battery systems.
Accordingly, an overcurrent protection device is needed that can be effectively applied to large battery systems.